The invention relates to a brakeband having two side bands portions which branch off from a central connecting portion in one circumferential direction of the axis of rotation of the brake and a middle band portion located axially between these two side band portions to branch off from it in the other circumferential direction. A thrust piece is located circumferentially adjacent to each of free band ends of the two side band portions, which are located opposite the connecting portion and circumferentially mutually confronting free end faces of the two side band portions and a band end of the adjacent thrust piece are welded to one another. It is considered advantageous that there are no circumferentially overlapping parts at the joints between band end and thrust piece, and that the inner faces of the two parts have a common constructional diameter during the operation of the brake.
In a known brakeband of this general type (U.S. Pat. No. 2,975,870), the two side band portions and the middle band portion each have the same width in the direction of the axis of rotation of the brake, even through the middle band works as the leading brake band end and therefore, because of the known especially high servo effect in a double-wound brakeband, is subjected to substantially higher stress than the two side bands portions together.
In a known brakeband of a different type (German Offenlegungsschrift 3,207,838), the thrust pieces are welded to the respective band ends in a circumferentially overlapping manner. There the thrust piece of the middle band portion is widened in the two directions of the axis of rotation of the brake and is thereby guided axially in corresponding recesses of the two side bands which are narrowed. The band ends of the two side bands are welded to a common thrust piece in an overlapping manner.
In a further known brakeband of a different type (G.B. Patent Specification 647,832), the middle band is twice as wide as each of the side bands. There the thrust pieces are made cuboid and are placed vertically on the outer face of the respective band ends and with their major axis radial to the axis of rotation of the brake.
The object of this instant invention is to make it possible to reduce the stress on the middle band, even when the latter is used as a leading brake band end, by increasing its band cross-section without at the same time having to increase the total width of the brakeband.
This object is achieved in an advantageous way by having the free band ends of side band portions widened in the direction of the axis of rotation of the brake in the axial direction pointing to the middle band and by having the middle band narrowed at its region located adjacent the connecting portion and axially oPposite the widened band end. The invention makes it possible to obtain a substantial widening of the middle band, because a sufficiently large weld-seam cross-section (at the juncture between the thrust piece and the free band ends) is still made available at the free band ends of the side bands, despite the narrowing of these bands necessary for the desired preservation of the total width of the brake band. The invention additionally affords the possibility of achieving a more favorable stress pattern in the connecting portion, at the transition between side bands and middle band, in the event that the brake band is stamped out of a one-part sheet metal pressing in such a way that the connecting portion is in one piece with the bands even in the final state of the brake band. Since the widened band ends are located in that band region of the middle band adjoining the connecting portion, this band region can be narrowed in such a way that the critical stress cross-section in the connecting portion is increased. The stress cross-section is limited by the transition of the axially inner side face of the associated side band into the connecting portion. As a result of the narrowing of the middle band, the transition of the side face of the middle band can be offset circumferentially by a larger amount (in relation to the transition of the said inner side face of the associated side band), which results in an increase of the above-mentioned critical stress cross-section between the said transitions to the connecting portion.
In the brake band according to the invention, the outlay in terms of material is no higher than in a normal two side band brake band.
In the brake band according to the invention, the danger of wear at the widened band ends of the side bands is reduced because the rigidity of these bands at their ends is increased.
Whereas, in the known brake bands described, the connecting portion (holding the middle and side bands together) forms a separate component which is either welded or connected in an articulated manner to the individual bands, in the brake band according to the invention, the connecting portion (together with the three individual bands) can form a one-piece sheet metal pressing, even in the finished state.
Whereas, in the referenced known brake bands, each of the three band ends is welded to a separate thrust piece, in the brake band according to the invention the band ends of the two side bands are welded to a common thrust piece.
In the brake band according to the invention, the middle band can advantageously have a width which is larger than the total width of the two side bands.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.